Isomerization linkage isomerism

Ionization isomerism Hydration isomerism Coordination isomerism Linkage isomerism Polymerization isomerism... 

In a second type of structural isomerism, linkage isomerism, the composition of the complex ion is the same, but the point of attachment of at least one of the ligands differs. Two ligands that can attach to metal ions in different... 

Figure 19 The [(NH3)5Co(N02)] complex, the first classical evidence for linkage isomerization. Linkage isomerism is normally promoted by light or change in temperature.

Ionization isomerism Hydiation isomerism Coordinatian isomerism Linkage isomerism... 

Sorbic acid could theoretically, by virtue of the two olefine linkages, exi.st in four geometrical I y-isomeric forms. The above synthesis gives only one form, which is undoubtedly the trans-trans form, analogous to the acu-diphenylpolyenes (p. 238) which are also normally produced solely in one form. 

Replacing one carbon atom of naphthalene with an a2omethene linkage creates the isomeric heterocycles 1- and 2-a2anaphthalene. Better known by their trivial names quinoline [91-22-5] (1) and isoquinoline [119-65-3] (2), these compounds have been the subject of extensive investigation since their extraction from coal tar in the nineteenth century. The variety of studies cover fields as diverse as molecular orbital theory and corrosion prevention. There is also a vast patent Hterature. The best assurance of continuing interest is the frequency with which quinoline and isoquinoline stmctures occur in alkaloids (qv) and pharmaceuticals (qv), for example, quinine [130-95-0] and morphine [57-27-2] (see Alkaloids). 

D-Glucose is produced by complete depolymerization of starch with enzymes that catalyze the hydrolysis of both its (1 — 4) and (1 — 6) linkages. Crystalline a-D-glucopyranose is generally sold as dextrose. Glucose is also isomerized to D-fmctose to produce high fmctose com symp (HFCS). 

Spectroscopy at variable temperatures enables us to reveal linkage isomerism of adsorption, when certain molecule fonu with the same site two or more complexes with different geometry and chemical properties. The most studied so far is the case of CO in zeolites, when besides the usual C-bonded complexes with the cations or OH-groups, energetically unfavorable O-bonded complexes ai e formed. 

Ambidentate ligands possess more than 1 donor atom and can coordinate through either one or the other. This leads to the possibility of linkage isomerism (p. 920). The commonest examples are the ions NO2 (p. 463) and SCN (p. 325). Such ligands can also coordinate via both donor sites simultaneously, thereby acting as bridging ligands. 

The rhodium and iridium complexes of dibenzothiophene (L) reveal an interesting case of linkage isomerism (91IC5046). Thus, the ti S) coordinated species [MCp LCb] on thermolysis with silver tetrafluoroborate afford the Ti -coordinated dicationic species. 

For this specific task, ionic liquids containing allcylaluminiums proved unsuitable, due to their strong isomerization activity [102]. Since, mechanistically, only the linkage of two 1-butene molecules can give rise to the formation of linear octenes, isomerization activity in the solvent inhibits the formation of the desired product. Therefore, slightly acidic chloroaluminate melts that would enable selective nickel catalysis without the addition of alkylaluminiums were developed [104]. It was found that an acidic chloroaluminate ionic liquid buffered with small amounts of weak organic bases provided a solvent that allowed a selective, biphasic reaction with [(H-COD)Ni(hfacac)]. 

Linkage isomerism in metal complexes. J. L. Burmeister, Coord. Chem. Rev., 1968. 3. 225-245... 

Rhodium, iodotetrakis(difluoro(diethylamino)-phosphine)-, 4, 924 Rhodium, pentaamminethiocyanato-base hydrolysis, 1, 504 Rhodium, pentaammincurea-linkage isomerism, 4, 961 Rhodium, pentaammine(urea)-decomposition, 1,186... 

Figure 16.18 summarizes the types of isomerism found in coordination complexes. The two major classes of isomers are structural isomers, in which the atoms are connected to different partners, and stereoisomers, in which the atoms have the same partners but are arranged differently in space. Structural isomers of coordination compounds are subdivided into ionization, hydrate, linkage, and coordination isomers. 

When D-fructose and L-sorbose are refluxed with aqueous HC1, dihexulose dianhydrides are formed.91 If the water is replaced by N./V-dimethylformamide, substantially increased yields are obtained and 1,2-linked disaccharides are detected. Higher yields of dianhydrides were obtained from fructose, rather than sorbose, under comparable conditions. Treatment of levan with dilute H2S04 at 60°C yielded92 a-D-Fru/-l,2 2,1 -fi-D-Fru/(5). Presumably, any products that contain 2,6-linkages with large central rings would rapidly isomerize to the more stable 1,2-linked product. 

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